The present invention relates to transmission tower erection and more particularly to apparatus for use in guiding an upper section of a tower onto a lower section. The present invention is directed to a novel and improved angle guide for detachable mounting on the receiving end of a lower section's structural support legs.
Transmission towers for supporting power lines may be erected to considerable heights, i.e., upwardly of 300 feet in some cases. The transmission towers are constructed of steel and typically comprise multiple sections, such as a lower section onto which an upper section is lowered prior to interconnection of the sections.
It has been found useful to utilize helicopters in the erection of the tower sections, and various proposals have been considered to facilitate the guiding of a suspended upper section onto a lower section. For instance, it has been proposed to mount so-called angle guides on each of the support legs of the lower section adjacent a top portion of the legs. The angle guides are inclined at an angle and each extends inwardly for several feet directed to a hypothetical apex of a pyramid. The upper section is provided with a cable or steel strap extending between lower portions of its support legs for contacting the angle guides as the upper section is being lowered. Upon contact, the upper section may be appropriately rotated by helicopter yaw movement so that its support legs contact an associated angle guide and slide therealong. The upper section's support legs may thereby be properly positioned adjacent associated support legs of the lower section. The support legs are then bolted together.
However, prior art angle guides are deficient from a number of standpoints. First of all, known angle guides are mounted to support legs of the lower section by means of bolts inserted through accommodating holes in the angle guide and the legs. The availability of properly positioned holes in the support legs which will mate with holes in the angle guide is always subject to doubt. Known angle guides must be provided with an excessive number of holes in an attempt to ensure that the angle guide may be mounted.
Additionally, known angle guides are not readily interchangeable for use in constructing either butt or overlap joints between the section legs. Thus, it is necessary to have different models of angle guides on hand in order to accommodate either type of joint construction.
Another problem present in prior art angle guides resides in the fact that inordinately long periods of time are required in order to mount and detach the guides. This problem results from the fact that considerable effort must be extended in locating suitable bolt holes or drilling accommodating holes in the guide. Unfortunately, drilling of holes in the support legs is oftentimes structurally unacceptable.
Accordingly, it is a general object of the present invention to provide an improved angle guide apparatus which may be detachably mounted, irrespective of bolt hole positioning, on a support leg of a lower tower section.
Another object of the present invention is to provide an improved angle guide which may be interchangeably used in constructing either butt or overlap joints between the suupport legs of the upper and lower sections.
Still another object of the present invention is to provide an improved angle guide which may be readily mounted and detached from support legs having different thicknesses. To this end, the present invention contemplates a clamp construction which enables the angle guide to be rigidly clamped to the support legs of the lower section.
Yet another object of the present invention is to provide an improved angle guide which is constructed with a detachable supporting ledge for limiting the extent to which a support leg of a upper section may be positioned relative to a support leg of a lower section. The supportive ledge finds particular utility in the construction of an overlap joint.
These and additional objects and advantages of the present invention will be more readily apparent from a consideration of the accompanying drawings and the following detailed description.